Papers by Keyword: Surface Energy

Abstract: Based on classical elasticity theory, the effects of surface stresses on the nanosized contact problem in an elastic half-plane which contains a nanocylindrical hole are analyzed. Meanwhile, the effects of surface energy of the contact nanosized surface are considered. The complex variable function method is applied to derive the fundamental solution of the contact problem. As example, the deformation induced by a distributed traction of cosine function on the nanosized surface is analyzed in detail. The results tell some interesting characteristics in contact mechanics, which are different from those in classical elasticity theory.

Abstract: In this study there was found that ionizing beta radiation increased the strength of bonded joints and improved the adhesion properties of polycarbonate (PC). Bonded joints at elevated temperature (60 °C) were tested. Generally, for the formation of quality bonded joint it is important to wet the adhesive bonding surface well. Wettability is characterized by the contact angle of wetting. The liquid has to have a lower surface energy than the solid in order to be able to wet the solid substance. The measurement results indicated that ionizing beta radiation was a very effective tool for improvement of adhesive properties and increased the strength of bonded joints of PC at elevated temperature (60 °C). Bonded surfaces with ionizing beta radiation doses of 0, 33, 66, 99, 132, 165 and 198 kGy were irradiated. The best results were achieved by irradiation at doses of 66 kGy by which the highest surface energy and the highest strength of bonded joints of PC were achieved. The strength of bonded joints after irradiation was increased up to 10 % and surface energy up to 30 % compared to untreated material.

Abstract: N-octadecyltrichlorosilane [OTS, CH₃(CH₂)₁₇SiC_l3] self-assembled monolayer (SAM) coatings were deposited on Si micromolds by dip-coating. Chemical composition, surface roughness, friction coefficient, thermal stability and surface energy of coatings were investigated. OTS coated silicon (Si) micromolds were used to fabricate PMMA microfluidic devices by hot-embossed process. All OTS coatings were thermally stable up to 180 °C, which is higher than hot-embossing temperature of PMMA. OTS coated micromolds had low friction coefficient, adhesion and superior molding efficiency, which improved lifetime of a uncoated Si micromold from 3 to 27 times.

Abstract: In this study there was found that radiation cross-linking increased the surface energy of high-density polyethylene (HDPE), and low-density polyethylene (LDPE). Surface energy affects the wettability of the surface and is very important for creating of high-quality bonded joints. The measurement results indicated that radiation cross-linking was a very effective tool for the improvement of adhesive properties and increased the surface energy of selected polyolefins. Surfaces of selected materials with ionizing beta radiation with doses of 0, 33, 66, 99, 132, 165, and 198 kGy were irradiated. The best results were achieved by irradiation at dose of 165 kGy. The surface energy after irradiation was increased up to 100 % compared to untreated material.

Abstract: The influence of the voltage of micro-arc oxidation on the physicochemical properties of the calciumphosphate coatings has been investigated. The linear growth of the roughness and hyperbolic decrease of the surface energy with growth of the oxidation voltage have been revealed. It was shown that the calciumphosphate coatings have low contact angle and high surface energy and, as a consequence, are hydrophilic. The optimal voltage range of the oxidation has been found. It varies from 200 to 250 V. This range provides the coating formation with the following specified parameters: surface roughness of 2 – 3.5 µm; contact angles with water and glycerol of 18 - 25º and 35 - 45º, respectively, and free surface energy of 73 - 80 mN/m.

Abstract: The stability and electronic properties of Mg₂Pb (100), (110) and (111) surfaces were investigated by using the first-principles density functional theory (DFT) method. The calculated results showed that the orders of relaxation and surface energy are |∆d₁₅(111)| < |∆d₁₅(110)| < |∆d₁₅(100)| and E_surf(100) > E_surf(110) > E_surf(111), respectively, indicating that Mg₂Pb (111) surface is the most stable among these three low index surfaces. The Density of states (DOS) of Mg₂Pb surfaces are mainly dominated by Pb-6, Mg-3s, and 2p orbitals in the band ranging from-5 eV to Fermi level. It can be further obtained from results of the DOS and the charge density difference that Mg₂Pb (111) surface is more stable than Mg₂Pb (100) and (110) surfaces. The Mg₂Pb (111) surface is the thermodynamically most favorable over all of the range of.

Abstract: The effect of substrate cleaning using ultrasonic cleaner on tungsten carbide was investigated. The surface energy of the substrate was measured using two liquids with dominant polar and dominant dispersion components which were distilled water (DI) and methylene iodide. Owens-Wendt method was carried out to calculate the surface energy of the substrate. The result showed that the cleaning process using solvent B (alkaline, DI, acid, DI, DI, alcohol) for 20 minutes without the wiping process led to the highest surface energy of 126.3399 dyne/cm with the polar component of 80.538 dyne/cm. Findings from this research suggested that type of solvent, cleaning time, and interactions among solvent type, cleaning time, and wiping process significantly influenced surface energy of the substrate.

Abstract: The plane surface energy of the mullite crystals (001), (010), (100) and (-100) is comparative calculated by using first-principles plane-wave pseudopotential method and the open hydrothermal system preparing mullite phase crystal test conditions. Also the plane growth habits can be predicted according to the results. The result shows that: the descending order of the mullite crystal surface energy is: E₍₀₀₁₎ > E₍₀₁₀₎ > E_(-100) > E₍₁₀₀₎. On the basis of Cune-Woolf principle, the surface energy of mullite crystals (001) surface is the maximum and growth rate is the fastest. Thus the (001) crystal face is growth surface habits of mullite phase crystal. Crystal growth morphology mostly extends in one direction.

Abstract: It is important to specify the Cu diffusion path in the oxide layer of a Cu/oxide/Pt-structured conducting-bridge random access memory (CB-RAM), in terms of both the elucidation of resistive switching mechanism and optimization of memory performance. A first-principle calculation is effective in specifying the Cu diffusion path with atomic resolution. However, reported results of first-principle calculations are based on too simplified model to depict the actual system of CB-RAM. In this paper, a periodic slab model for the first-principle calculation of Cu diffusion process in HfO₂-CB-RAM was proposed based on experimental results. Both the most probable Cu diffusion surface and Cu diffusion path were suggested by the first-principles calculations based on the model. It was also suggested that the Cu diffusion path was modified by introducing oxygen vacancy into the Cu diffusion surface.

Abstract: As examples of the most typical methods to determine the shear strength of SiC/SiC composite joints, the asymmetrical four point bending test of a butt-joined composite, the tensile test of a lap-joined composite, and the compression test of a double-notched composite joint were analyzed by using a finite element method with the interface element. From the results, it was found that the shear strength in the asymmetrical bending test was controlled by both the surface energy and the shear strength at the interface regardless of their combination while the strength in the tensile test or the compression test was governed by the surface energy when both the surface energy and the shear strength were large. In addition, the interface element was employed in order to examine the influence of the specimen geometry on the microstructural fracture morphology in nanoSiC/SiC composite during a miniaturized Double Notch Shear (DNS) test. From the serial computations, it is revealed that a relationship between the inter-laminar shear strength and the yield stress seems to be very important for selecting appropriate specimen geometry of the miniaturized DNS test.